Effects of oxidation temperature, time, and ambient pressure on the oxidation of ZrB2–SiC–graphite composites in atomic oxygen

The effects of oxidation temperature, time, and ambient pressure on the oxidation of ZrB2–SiC–graphite composites in atomic oxygen were investigated. The phase formation oxidized in atomic oxygen was similar to that of ZrB2–SiC–graphite composites oxidized in air up to 1600 °C. However, the ZrO phase that formed at 1600 °C in atomic oxygen was specific to the higher temperature treatment and the amount of this phase increased with increased oxidation time. The weight gain per unit surface area as a function of oxidation time exhibited a parabolic to linear kinetic behavior. Compared with specimens oxidized in air, the glass-phase layer that formed at 1600 °C in atomic oxygen was not thick enough to fill the holes on the exposed surface. The mechanical properties of ZrB2–SiC–graphite composites oxidized in atomic oxygen decreased with increased oxidation temperature, time, and ambient pressure. These results can facilitate the expanded application of UHTCs.